Electrical contact assembly

ABSTRACT

Electrical contact assembly having at least four contact structures. Each contact structure is positioned around a centering bolt. Compressed springs are located between each inner contact structure and between the upper contact structure and the upper end of the centering bolt. A sleeve is located between the lower contact structure and the lower end of the centering bolt. The centering bolt extends through openings in a contact carrier. Movement of the contact structures in a direction parallel to the axis of the centering bolt is provided by changing the compression of the springs and/or moving the centering bolt.

United States Patent [1 1 Guidosh ELECTRICAL CONTACT ASSEMBLY Edward F. Guidosh, Hubbard, Ohio Westinghouse Electric Corporation, Gateway Center, Pittsburgh, Pa.

Oct. 27, 1972 Inventor:

Assignee:

[22] Filed:

Appl. No.1

3,396,248 8/1968 Wilson 200/11 13 3,192,328 6/1965 Wilson 200/11 B FOREIGN PATENTS 0R APPLICATIONS 1,204,810 9/1970 Great Britain 200/11 TC Dec. 18, 1973 Primary ExaminerDavid Smith, Jr. Assistant Examiner-William .1. Smith Attorney-A. T. Stratton et al.

[57] ABSTRACT Electrical contact assembly having at least four contact structures. Each contact structure is positioned around a centering bolt. Compressed springs are located between each inner contact structure and between the upper contact structure and the upper. end of the centering bolt. A sleeve is located between the lower contact structure and the lower end of the centering bolt. The centering bolt extends through openings in a contact carrier. Movement of the contact structures in a direction parallel to the axis of the centering bolt is provided by changing the compression of the springs and/0r moving the centering bolt.

6 Claims, 3 Drawing Figures ELECTRICAL CONTACT ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical contact assemblies and, more specifically, to electrical contact assemblies having a plurality of floating contact structures.

2. Description of the Prior Art Electrical contact assemblies used in power transformer tap changers must be capable of conducting a relatively large amount of current. Many prior art contact assemblies used intap changers include two contacts which are forced together against the terminals they connect together. With this arrangement, substantially one-half of the current is conducted by each contact.

When a relatively large current conducting capacity is required, larger or additional contacts must be used. Either arrangement requires considerable space in the tap changing apparatus. It is desirable, and it is an object of this invention, to provide a high capacity contact assembly wherein the space required by the contacts thereof is as small as practicable.

Electrical contacts of the'type used in tap changers usually are moved in an are around a terminal ring. One portion of the contact-continuously touches the terminal ring. Another portion of the contact alternately engages and disengages with stationary terminals located in the path of the arc traversed by the contact assembly. To provide proper engagement, some means must be provided to permit the alignment of the contacts with the stationary terminals. Therefore it is desirable, and it is an object of this invention, to provide a high capacity contact assembly having a plurality of contact structures which may be moved sufficiently to permit satisfactory engagement with stationary terminals.

SUMMARY OF THE INVENTION There is disclosed herein a new and useful electrical contact assembly suitable for use in high current tap changerss'lhe electrical contact assembly includes a contact carrier having two openings through which a centering bolt extends. At least four contact structures are located around the centering bolt and are slidable thereon. A first compressed spring is located between the inner contact structures. A second compressed spring is located between the upper end of the center ing bolt and the upper contact structure. A sleeve is located between the lower end of the centering bolt and the lower contact structure. Each of the four contact structures are movable in-a direction parallel to the axis of the centering bolt. Movement of either the upper or lower contact structure changes of the force exerted by the second spring. When the lower contact structure moves, the centering bolt moves also. Movement of either of the inner contact structures changes the force exerted by the first spring. The arrangement taught by this invention permits the construction of a high capacity contact assembly which requires a minimum amount of sapce. Placing additional contact structures and springs'around the centering bolt is within the contemplation of this invention.

Y BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG. I is a partial plan view of a tap changer contact and terminal arrangement;

FIG. 2 is an exploded view of an electrical contact as sembly constructed according to this invention; and

FIG. 3 is a sectional elevation view of an electrical contact assembly constructed according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description, similar reference characters refer to similar members in all figures of the drawing.

Referring now to the drawing, and FIG. I in particular, there is shown a portion of a transformer tap changer. An electrical contact assembly 10 is attached to a rotatable arm 12. The contact assembly 10 includes contacts, such as contact 14, which engage with a terminal ring 16 and with one of the stationary terminals 18. The terminal ring 16 and the stationary terminals 18 are electrically connected to other associated electrical apparatus such as a transformer winding or bushing. When the arm 12 swings the contact assembly 10 through an arc, the contact assembly 10 engages with the other stationary terminals 18 which are attached to the mounting member 19.

FIG. 2 is an exploded view of the contact assembly 10. The assembly 10 includes the contact carrier 20 which contains an upper opening 22 and a lower opening which is not shown in FIG. 2. The lower portion of the contact carrier 20 also includes a projection 24 which contains a threaded opening to permit attachment of the contact carrier 20 to the arm 12. Although other materials may be used, the contact carrier 20 may be constructed of a metallic material such as steel.

The contacts 14, 26, 28 and 30 are constructed of a good electrical conducting material such as copper. A suitable material, such'as coin silver, may be disposed on the contacts to form conducting surfaces, such as the surfaces 32 and 34 on contact 26. Each of the contacts 14, 26, 28 and 30 contains an opening, such as the opening 36 in contact 14. The contacts 14, 26,

28 and 30 are associated with saddles 38, 40, 42, and v 44, respectively. The saddles 38, 40, 42 and 44 help guide the contacts within the contact carrier 20 and form wells, suchas well 43, which provide convenient regions for the location of other members of the contact assembly 10.

A centering bolt 46 is positioned through the upper opening 22, through openings, such as the opening 36, in the contacts 14, 26, 28 and 30, and through a lower opening in the contact carrier. The first or upper end 48 of the centering bolt includes a head 52 against which a coil spring 54 is positioned.

When the members are assembled, such as shown in FIG. 3, the coil spring 54 extends through the opening 22 and through the opening 56 in the saddle 38, and the coil spring 54 is positioned against the contact 14. A coil spring 58 is positioned around the centering bolt 46 and is compressed between the contacts 26 and 28. The second or lower end 50 of the centering bolt is attached to a suitable restraining means, such as the nut 60 and the sleeve 62.

FIG. 3 illustrates, in section, an assembled contact assembly constructed according to this invention and FIG. 3 will be used in describing the operation thereof. The contact assembly 10 is shown in engagement with the terminal ring 16 and the stationary terminal 18. FIG. 3 also illustrates an insulating spacer 66 positioned between the spring 58 and the contact 26 to prevent the conduction of large currents through the spring 58. Spring 58, as well as spring 54, could also be coated with an insulating material, such as epoxy.

When the contact assembly 10 is moved to disengage from the terminal 18, the conducting surfaces of adjacent contacts, such as surfaces 32 and 32', are forced together since the springs 54 and 58 are assembled in a compressed state. Adequate space is provided between the contacts and the centering bolt 46 to allow a slight unparallel movement of the contacts with respect to each other. Upon. engagement to produce the condition shown in FIG. 3, adjacent contacts must move apart. When the upper portion 68 of the terminal 18 is not centered with the adjacent contacts 14 and 26, one of the contacts must move, during engagement, a greater amount than the other contact in a direction which is transverse, or parallel, to the axis of the centering bolt. A similar requirement exists when the contacts 28 and 30 engage with the lower portion 70 of the terminal 18.

The openings 32 and 72 in the contact carrier 20 are sufficiently large enough to permit movement of the centering bolt 46 transversely with respect to its longitudinal axis. The extent of this movement is limited by the distance between the saddles 38 and 44 and the contact carrier 20. The overall effect of the arrangment illustrated is to provide a contact assembly 10 wherein each of the contacts 14, 26, 28 and 30 are floating, that is, transversely movable to allow engagement and to allow the terminal misalignment.

A limited amount of simultaneous movement of all four ofthe contacts 14, 26, 28 and 30 is provided by the transverse movement of the centering bolt 46. When less than all four of the contacts 14, 26, 28 and 30 are moved simultaneously, one of the springs 54 or 58 must be compressed further. When the contact 14 is raised, that is, moved in a direction which is toward the centering bolt end 48, the spring 54 is compressed further. When the contact 26 is lowered, that is moved in a direction which is toward the centering bolt end 50, or when the contact 28 is raised, the spring 58 is compressed further. Spring 54 is also further compressed when the contact 30 is lowered. The sleeve 20 slides witin the opening 72 and helps center the centering bolt 46 within the opening 72. The bolt 46 is centered in the opening 32 by the spring 54 and, when the bolt is lowered, by the bolt head 52.

The invention disclosed herein provides a floating contact assembly having a minimum number of components contained in a minimum amount of space. Additional contacts may be used within the contemplation of this invention. For example, the centering bolt 46 and the contact carrier 20 may be longer than shown in-FlG. 3. With the longer members, an additional pair of contacts may be inserted between the sleeve 62 and the contact 30, along with an additional spring position between the new contacts and the contact 30.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended thatall of the matter contained in the foregoing description or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

l claim as my invention:

1. An electrical contact assembly comprising:

a contact carrier having openings therein;

a centering bolt having first and second ends, said centering bolt being movably positioned in the openings of said contact carrier;

first, second, third and fourth contacts each having an opening therein through which said centering bolt extends;

means for forcing said first contact away from the first end of said centering bolt;

means for forcing said second contact toward the first end of said centering bolt and for forcing said third contact toward the second end of said centering bolt; and

means for maintaining a predetermined distance between said fourth contact and the second end of said centering bolt.

2. The electrical contact assembly of claim 1 wherein the means for forcing said first contact away from the first end of the centering bolt comprises a compressed coil spring which is positioned around the centering bolt and between the first end of the centering bolt and the first contact.

3. The electrical contact assembly of claim 1 wherein the means for forcing the second contact toward the first end of the centering bolt and for forcing the third contact toward the second end of the centering bolt comprises a compressed coil spring which is positioned around the centering bolt and between the second and third contacts.

4. The electrical contact assemblypfjclaim 3 wherein an insulating member is located at one end of the compressed coil spring.

5. The electrical contact assembly of claim 1 wherein the means for maintaining a predetermined distance between the fourth contact and the second end of the centering bolt comprises a sleeve restrained at the second end of the centering bolt, said sleeve extending through one of the openings in the contact carrier and abutting a face of the fourth contact.

6. An electrical contact assembly for tap changer comprising:

a contact carrier having upper and lower openings therein;

first, second, third and fourth contact structures each containing an opening therein;

a longitudinal centering bolt extending through the openings in said first, second, third and fourth contact structures, and the openings in said contact carrier the diameter of said centering bolt being suitably dimensioned to allow the sliding of said first, second, third and fourth contact structures with respect to said centering bolt;

a first compressed coil spring positioned around said centering bolt and located between the first end of said centering bolt and said first contact structure;

a second compressed coil spring positioned around said centering bolt and located between said second and third contact structures; and

means for maintaining a predetermined distance between said fourth contact structures and the second end of said centering bolt. 4: 

1. An electrical contact assembly comprising: a contact carrier having openings therein; a centering bolt having first and second ends, said centering bolt being movably positioned in the openings of said contact carrier; first, second, third and fourth contacts each having an opening therein through which said centering bolt extends; means for forcing said first contact away from the first end of said centering bolt; means for forcing said second contact toward the first end of said centering bolt and for forcing said third contact toward the second end of said centering bolt; and means for maintaining a predetermined distance between said fourth contact and the second end of said centering bolt.
 2. The electrical cOntact assembly of claim 1 wherein the means for forcing said first contact away from the first end of the centering bolt comprises a compressed coil spring which is positioned around the centering bolt and between the first end of the centering bolt and the first contact.
 3. The electrical contact assembly of claim 1 wherein the means for forcing the second contact toward the first end of the centering bolt and for forcing the third contact toward the second end of the centering bolt comprises a compressed coil spring which is positioned around the centering bolt and between the second and third contacts.
 4. The electrical contact assembly of claim 3 wherein an insulating member is located at one end of the compressed coil spring.
 5. The electrical contact assembly of claim 1 wherein the means for maintaining a predetermined distance between the fourth contact and the second end of the centering bolt comprises a sleeve restrained at the second end of the centering bolt, said sleeve extending through one of the openings in the contact carrier and abutting a face of the fourth contact.
 6. An electrical contact assembly for tap changer comprising: a contact carrier having upper and lower openings therein; first, second, third and fourth contact structures each containing an opening therein; a longitudinal centering bolt extending through the openings in said first, second, third and fourth contact structures, and the openings in said contact carrier the diameter of said centering bolt being suitably dimensioned to allow the sliding of said first, second, third and fourth contact structures with respect to said centering bolt; a first compressed coil spring positioned around said centering bolt and located between the first end of said centering bolt and said first contact structure; a second compressed coil spring positioned around said centering bolt and located between said second and third contact structures; and means for maintaining a predetermined distance between said fourth contact structures and the second end of said centering bolt. 